PLANT-GROWTH REGULATOR EFFECTS ON PROTEIN-CONTENT AND YIELD OF SPRINGBARLEY AND WHEAT

Plant growth.regulators (PGR) have potential to increase grain yield a nd may also alter grain protein levels of cereal crops. A 3-yr field e xperiment with spring barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) cultivars was conducted to determine whether ethephon tre atment increased protein concentration, protein yield, and grain yield . A greenhouse experiment was also conducted to evaluate the response of barley grain protein concentration to gradual addition of ethephon (2.2 x 10(-3) mM) or chlormequat (5.8 x 10(-3) mM) solution after anth esis. Under field conditions, ethephon treatment increased barley and wheat grain protein concentrations by as much as 16 % but decreased gr ain yield so that protein yield increases were small or did not occur. For Laurier barley, total grain N content was increased by up to 20 % in one year of this study. However, over the 3 years, an inverse rela tion existed between grain protein and yield. Greenhouse data showed t hat i) the gradient in grain size and protein concentration among spik elets of a spike, which is established before anthesis, was not affect ed by either chlormequat or ethephon; and ii) chlormequat increased gr ain protein by 7 to 11 % whereas ethephon increased protein concentrat ion by up to 13 % in one of the two experiments. Our data indicate tha t PGR can alter protein accumulation in the grain, and thus, the quali ty of bread wheat and feed barley crops can be increased in regions wi th a short crop-growing season. However, a portion of the increase in grain protein concentration is due to decreased starch deposition, whi ch is associated with yield reductions. The greenhouse data confirmed that a portion of the increase in grain protein concentration due to P GR application is caused by increased protein accumulation in the barl ey grain.